1. Field of the Invention
The present invention relates to a semiconductor memory device and a manufacturing method thereof, and more particularly, to a semiconductor memory device including a capacitor structure and a manufacturing method thereof.
2. Description of the Prior Art
Dynamic random access memory (DRAM) is a kind of volatile storage device which is an indispensable key part of many electronic products. DRAM includes a great number of memory cells arranged for forming an array configured to store data. Each of the memory cells may be composed of a metal oxide semiconductor (MOS) transistor and a capacitor connected in series.
The density of the memory cell has to be increased for the product demands, and the difficulty and the complexity of the related processes and design become higher accordingly. For instance, the area occupied by the capacitor structure in the memory cell becomes smaller relatively when the density of the memory cell increases. The capacitor structure has to extend upwards for increasing the area of the electrode in the capacitor structure because of the demand for a specific capacitance. However, it is very difficult to form an electrode layer having an extremely high aspect ratio when the height of the capacitor structure increases, and the manufacturing yield cannot be improved accordingly.